Compressed air supply systems of this kind have at least one first compressed air network, which supplies a pneumatic brake system of the truck trailer with an air pressure limited according to EU-wide legal requirements. Compressed air supply systems of this kind for truck trailers furthermore have at least one compressed air supply coupling between the tractive vehicle and the truck trailer for supplying compressed air.
Owing to the limited air pressure, which must be maintained via a compressed air coupling to the truck trailer for a pneumatic brake system on the basis of EU-wide legal requirements, it is not possible using compressed air couplings of this kind to supply automatic tire pressure control systems for the truck trailer, for example. This is because tire pressure control systems require a significantly higher pressure, especially as it is the task of a tire pressure control system to set in an optimum manner an optimum tire pressure while underway, in accordance with the characteristics of the road, the vehicle speed, the vehicle loading, the outside temperature and the extrapolated tire and road surface temperatures, even while underway, by increasing or reducing the tire pressure in the rotating wheels.
Known tire pressure valves are based on the assumption that the tire pressure will be adapted to the corresponding environmental conditions when the vehicle is stationary. This means that the vehicle must interrupt the journey and that the tires will have to be adapted individually and manually to an optimum tire pressure by the vehicle driver. To do this, the practice up to now has been to visit appropriate service stations that have appropriate fixed high-pressure systems in order to provide the compressed air requirement at high pressure.
In order to meet the requirement for regulation of the tire pressure even while underway, not only are special tire pressure control valves required but there is also a need for an appropriate high-pressure supply to the vehicle trailer in order to supply the vehicle trailer with appropriate pressure energy.
U.S. Pat. No. 6,269,691 B1 discusses an automatic tire pressure supply system with a booster pump driven by a compressed air supply having a limited air pressure via the permitted compressed air coupling of the truck trailer. The booster pump consumes a volume of compressed air at the limited air pressure in order to transform compressed air into a higher output pressure for a tire pressure control system since the tires require a higher air pressure than is permitted by a first compressed air network for supplying the brake system of truck trailers. A pressure surge protection valve and a pressure relief valve are additionally provided in the system for a known tire pressure supply and control system of this kind with an additional booster pump in order to ensure smooth operation of the compressed air supply system for the truck trailer.
A compressed air supply system of this kind has the disadvantage that an additional compressor with appropriate additional protection and pressure relief valves has to be provided in the trailer to make available the higher pressure for a tire pressure control system, for example, and to supply an appropriate second high-pressure network in the truck trailer with an appropriate higher air pressure.